Maybee, you are traveling to Barcelona and have not more time to travel to France or other countries.
I tell you a nice place in Barcelona for eat french cuisine. It's my favorite place for eat the Onglet and the best place in Barcelona for the Steak Tartare.
The name from the Place is L'Office, the webpage is http://www.officebcn.com , it's a small place, not for groups, wich recreate the original french bistrot in Barcelona.
My recomendation are scrambled eggs with truffles, the onglet and the Steack Tartare (Choped Hanger Steak).
They have also a big selection of french and spanisch wines.
I hope you try the place and maybe you confirm here my post. :)
I found Chowhound a nice place, because i can get there local tips from nice places, sometimes when we arrive in on place is a big problem to find good quality places to eat, and is everytime nice i thing when we ge some tips :)